1. Field of the Invention
This invention relates to the fields of dumping vehicles and handling devices for various containers carried on dumping vehicle chassis. In particular, the invention is a trailer for a tractor/trailer configuration adapted to dump the contents of containers as well as to unload and re-load the containers themselves onto and off of the chassis.
2. Prior Art
Vehicle chassis are known in which a container or a platform permanently attached to the chassis can be inclined for dumping. In U.S. Pat. No. 986,604 to Stuckwisch, a two-axle wagon has a suspension which is adapted to fold under a box for a load, at a fulcrum forward of the load's center of gravity, causing the wagon to dump to the rear. U.S Pat. No. 647,284 to Wetmore also discloses a dumping arrangement wherein the axles of a wagon are displaceable to approach one another during dumping; however, this is done by a slide mount for one axle and not by means of a pivoting knuckle at a more or less central portion in the chassis.
British Patent No. 1,594,063 to Lloyd et al, teaches a trailer for small garden tractors and the like, having two frames pivotably attached to one another at a pivot point above the chassis and above the load area. By manipulating a draw bar connected to the pivoting linkage, the user causes the load-carrying chassis to pivot, dumping the contents. U.S. Pat. No. 4,417,841 to Chadwick teaches a complex dumping vehicle having a plurality of extendable cylinders that tilt a load bed section relative to a carrying bed section, the carrying bed section having articulated means that become angularly displaced in the dumping process.
The foregoing references teach various aspects of dumping. The present invention is concerned not only with dumping, but also with applying the technology of dumping to discrete standardized containers such as flat beds, tanks, bulk material containers and the like, which are attachable to a vehicle chassis via standardized connectors located at predetermined positions. The invention is especially useful for shipping containers of the type identified in the art as "containerized freight" containers. These containers, which are variously described as freight containers, cargo containers and intermodal containers, can be loaded and sealed, the cargo being protected from origin to destination. The containers are large heavy-duty boxes in standard lengths, which normally occupy the entire area defined by the chassis of a tractor trailer. The "chassis" itself is simply a frame (excluding floor, sides and roof) carried on wheels and having locking devices for securing and transporting a container as a wheeled vehicle. The containers can be transferred between trucks, railroad cars and ships using special purpose lifting and transfer equipment, and container securing devices, which have evolved to engage the containers by their corners. For mounting the shipping containers on a container chassis of a tractor trailer, the four lower corners of the container are provided with reinforced receptacles for mating with fixing pins mounted on the rigid trailer chassis, the pins protruding vertically from the load bed defined by the chassis. In transferring the shipping container to the chassis, transfer equipment which may have lifted and transferred a container, for example from a ship, a railroad car or another truck, aligns the container with the fixing pins on the chassis and simply lowers the container into place, thereby fixing the container against horizontal displacement relative to the chassis. It is possible to add horizontally operable locking means to the vertical pins, for example by means of a twist-lock arrangement whereby an asymmetrical locking pin head is twisted in a complementary hole in the container, and thereby ensure that the container also remains vertically fixed on the chassis due to the pins even if the chassis is upset. Twist lock fixing pins are known with pneumatic controls for twisting the pins to lock or unlock the container. The pins are relatively long and substantial and hold the container against any horizontal displacement on the chassis during jostling encountered in over-the-road travel.
A large number of these discrete containerized freight shipping containers have been produced. The containers are easily manipulated using the specialized transfer machinery adapted for engaging them, but such transfer machinery is so large and specialized that it is only feasible where a large number of containers will be transferred, for example at shipping ports served by railroad. The transfer equipment is not generally available to small scale or infrequent users of the shipping containers. While it is possible to employ general purpose lifting and transfer devices to the containers (e.g., construction cranes, large forklift trucks, etc.), this is cumbersome and even these general purpose devices become large and expensive when designed with the typical hydraulic machinery and high capacity load-bearing equipment required to handle the large and heavy loads of full shipping containers. As a result, use of the containers has been limited apart from overseas shipping and incidental transport to their ultimate destination. A large number of standardized shipping containers accumulate unused at shipping ports or used as stationary storage enclosures, even though these containers are structurally sound and fully capable of use for transporting goods and materials. It is simply not cost effective for the owners of shipping containers or the small or infrequent terminals which could use them, to invest in large capacity equipment which is economically feasible in connection with large transfer ports handling thousands of containers over a given time period but not where only a few containers are likely to be handled in the same time.
The same sort of mountings used for "containerized freight" boxes are also used to adapt standard chassis to standard containers of other types, also attached to the chassis via pins. Accordingly, the description of "containers" herein also applies to containers which are open at the end or top, open at all the sides (i.e., a platform or flat-bed), adapted for fluid or bulk-pourable loads (i.e., tanks), and the like. As appropriate to their loads, the containers may be steel, aluminum, fiberglass-reinforced plywood ("FRP") or combinations of such materials. All these types of containers have been standardized and thus made interchangeably fittable to a standardized chassis.
There is a need to facilitate loading and unloading all forms of containers and/or contents of the containers, using equipment that is readily available and does not involve a great deal of expense, being inherently inexpensive, and capable of productive uses other than simply loading, carrying and unloading particular types of containers.
Trailer chassis for tractor/trailer configurations in use for carrying standardized containers are relatively uncomplicated. A standard king pin assembly for articulating the chassis to a motorized tractor includes a large pin (the "king pin") protruding vertically downward from one end of the trailer chassis. The king pin engages in a king pin-receiving frame on a rear deck of the tractor chassis. One or two four-wheel tire axles are located at the rear of the trailer chassis, and means can be provided on the trailer chassis for displacing the wheel axles forward and backward along the chassis to accommodate a particular load rating. The structural components of known trailer chassis are rigid beams and cross members which can be angle stock, channels, I-beams or the like. Supplemental supporting feet are located toward the front of the trailer chassis and can be manually extended such that the trailer will support itself apart from the tractor. The chassis includes means for electrical wiring for lights and the like, and conduits for pneumatic controls, especially for the rear brakes. In other respects, the typical trailer for carrying standardized shipping containers is simply a frame-work of steel beams and cross-members, with upwardly-protruding fixing pins for mating with the corner sections of the container.
The present invention revises the known container-carrying trailer chassis (or possibly front-wheel-drive truck chassis with fixed bed) to enable dumping the contents of any form of container through rear openings therein, for example through doors in an end wall of the container, and also concerns providing means for loading and unloading whole containers of any of the standardized types on the chassis, without a large transfer apparatus or heavy duty crane or lift adapted to engage the containers for transfer. Instead, according to the invention the containers are loaded and unloaded or dumped primarily with the assistance of gravity and inclined planes produced by a pivoting knuckle-like arrangement articulating the otherwise-rigid trailer chassis and controllably causing the chassis to assume a centrally humped configuration at the knuckle. The knuckle is placed forward of the container center of gravity such that the container is carried along with a rear section of the chassis, which inclines to the rear, and thus enabling either unloading of contents (the container being retained on the chassis via its fixing pins when tilted), or unloading or re-loading of the container itself by sliding the whole container off to the rear or back on from the rear (the fixing pins being retracted). The invention thus opens the door for small scale container users because all the necessary transfer apparatus is included in the trailer chassis. Currently unused shipping containers can thus be put into service, exploiting the benefits of the shipping containers apart from expensive transfer equipment (which of course can still be used where available). Trailer chassis are more practically capable of use with different forms of containers, e.g., flat beds, contoured beds, stakes, liquid tanks, bulk tanks and boxes with or without all their walls. This is achieved without re-manufacturing the chassis or container for each change and without difficult container transferring steps using load carrying equipment. Nor does the capability add substantially to the cost of a container-carrying chassis.
Of course the invention can be applied to new chassis construction or existing chassis can be modified. Inasmuch as existing chassis have the rigid components needed for the front and rear portions of the chassis to be articulated, adapting an existing chassis to the invention involves inserting a knuckle, pivotable king pin plate and drive means. The drive means can be varied as needed for adequate capacity, using an electric winch or a hydraulic winch with a block and pulley system, or using one or two hydraulic retracting rams.
For true general purpose applicability, the chassis can include fixing pins spaced or dimensioned for different types and lengths of shipping containers. The containers, for example are standard in lengths of twenty, thirty-five and forty feet. While the invention is preferably embodied to include an electrical winch driven system for driving the trailer chassis to incline around its knuckle, the user can if desired choose a hydraulic pump "wet line" system or modify an electric winch system after initial manufacture.